I am installing and configuring Exchange 2013 on a Dell PowerEdge T420. It has 2 x Intel Xeon CPU E5-2420 processors and 16GB of RAM. I am using ESXi VMware Hypervisor 6.0.0. for virtualizing the servers. Currently I have two Windows Server 2012 R2 servers installed. Server1 is configured as Domain Controller. Server2 will host Exchange 2013. Should I install a Domain Controller and AD on Server2 and then install Exchange 2013 on top of it, or should I just install Exchange 2013 on this second server, which would be the best practice? Each virtual server has 8GB of with 8 core CPUs.